The present invention relates to polyamide resins having exceptionally high impact strength prepared by forming an interpolymer of at least one polyamide forming monomer with a mixture comprising a low molecular weight diolefin polymer and a dimerized fat acid or derivative thereof, said diolefin polymer and dimerized fat acid or acid derivative having terminal amide-forming functional groups on each end of the molecular chain.
Polyamide resins have long been known for their excellent toughness, flexibility, abrasion resistance and relatively good impact strength. Molded or extruded polyamides in general have found applications in appliances, consumer products, electronics, machine components, automotive parts, gears and like uses.
Although the polyamides are noted for their toughness and relatively good impact strength, there are many speciality applications where exceptional strength is required. These specialty applications include automotive uses of molded parts formed from polyamides such as bumpers, deflection shields, light shields, and like items which at times may be subject to severe impact from external sources. Thus, whereas the most popular polyamides in terms of price and availability, e.g., polycaprolactam or polyhexamethylene adipamide, are generally suited for most applications, there is some reluctance in using these and other materials in applications where exceptional impact resistance is a requirement.
Various attempts have been made in the prior art to increase the impact strength of polyamides. The most common technique involves plasticization. However, plasticizers may deleteriously affect other properties such as processing behavior, modulus and tensile strength to the point where the advantage of moderatley increased impact strength is outweighed by these disadvantages. Other techniques for improving impact strength involves blending polyamide resins with other polymers such as ethylene/alkyl acrylate copolymers as disclosed in U.S. Pat. No. 3,472,916, or ethylene/ unsaturated carboxylic acid copolymers as disclosed in U.S. Pat. No. 3,236,914. U.S. Pat. No. 3,388,186 discloses polylactams of improved impact strength prepared by polymerizing the lactam monomer in the pressure of a minor amount of an ethylene copolymer containing acid groups. Other methods for improving impact strength of a given polyamide homopolymer such as polycaprolactam or polyhexamethylene adipamide include the formation of higher molecular weight copolymers of the relevant monomer or salt with other specific polyamide forming monomers or their salts, which yield polymers of impact strength higher than the given polyamide hompopolymer. Although these and other impact modification techniques are effective, the availability of raw materials, the increased complexity of preparation, or cost considerations are mitigating factors toward their wide acceptance.
Accordingly, it is an object of this invention to provide polyamide polymers having improved mechanical properties.
A more specific object is to provide polyamide polymers having high resistance to impact.